Based on feedback in PR https://github.com/swiftlang/swift/pull/69460, enabling indexing for synthesized decls because they are usable by users and make sense to appear in the indexstore.
Sets `synthesized` on some additional decls:
- derived `hashInto(...)`
- Objc properties and methods derived from Objc protocols
https://github.com/apple/swift/issues/67446
Add new `-print-ast-decl` frontend option for only printing declarations,
to match existing behavior.
Some tests want to print the AST, but don't care about expressions.
The existing `-print-ast` option now prints function bodies and expressions.
Not all expressions are printed yet, but most common ones are.
Do not mark synthesized `TangentVector` members as synthesized so that the type checker won't sort them. We would like tangent vector members to have the same order as the properties in the parent declaration.
Also add `typealias TangentVector = Self` to the synthesized `TangentVector` so that it will not need its own `Differentiable` conformance derivation.
Resolves SR-14241 / rdar://74659803.
Compiler:
- Add `Forward` and `Reverse` to `DifferentiabilityKind`.
- Expand `DifferentiabilityMask` in `ExtInfo` to 3 bits so that it now holds all 4 cases of `DifferentiabilityKind`.
- Parse `@differentiable(reverse)` and `@differentiable(_forward)` declaration attributes and type attributes.
- Emit a warning for `@differentiable` without `reverse`.
- Emit an error for `@differentiable(_forward)`.
- Rename `@differentiable(linear)` to `@differentiable(_linear)`.
- Make `@differentiable(reverse)` type lowering go through today's `@differentiable` code path. We will specialize it to reverse-mode in a follow-up patch.
ABI:
- Add `Forward` and `Reverse` to `FunctionMetadataDifferentiabilityKind`.
- Extend `TargetFunctionTypeFlags` by 1 bit to store the highest bit of differentiability kind (linear). Note that there is a 2-bit gap in `DifferentiabilityMask` which is reserved for `AsyncMask` and `ConcurrentMask`; `AsyncMask` is ABI-stable so we cannot change that.
_Differentiation module:
- Replace all occurrences of `@differentiable` with `@differentiable(reverse)`.
- Delete `_transpose(of:)`.
Resolves rdar://69980056.
Differentiable conformance derivation now "peers through" property wrappers.
Synthesized TangentVector structs contain wrapped properties' TangentVectors as
stored properties, not wrappers' TangentVectors.
Property wrapper types are not required to conform to `Differentiable`.
Property wrapper types are required to provide `wrappedValue.set`, which is
needed to synthesize `mutating func move(along:)`.
```
import _Differentiation
@propertyWrapper
struct Wrapper<Value> {
var wrappedValue: Value
}
struct Struct: Differentiable {
@Wrapper var x: Float = 0
// Compiler now synthesizes:
// struct TangentVector: Differentiable & AdditiveArithmetic {
// var x: Float
// ...
// }
}
```
Resolves SR-12638.
Previously, two conditions were necessary to enable differentiable programming:
- Using the `-enable-experimental-differentiable-programming` frontend flag.
- Importing the `_Differentiation` module.
Importing the `_Differentiation` module is the true condition because it
contains the required compiler-known `Differentiable` protocol. The frontend
flag is redundant and cumbersome.
Now, the frontend flag is removed.
Importing `_Differentiation` is the only condition.
Add `AdditiveArithmetic` derived conformances for structs and classes, gated by
the `-enable-experimental-differentiable-programming` flag.
Structs and classes whose stored properties all conform to `Differentiable` can
derive `Differentiable`:
- `associatedtype TangentVector: Differentiable & AdditiveArithmetic`
- Member `TangentVector` structs are synthesized whose stored properties are
all `var` stored properties that conform to `Differentiable` and that are
not `@noDerivative`.
- `mutating func move(along: TangentVector)`
The `@noDerivative` attribute may be declared on stored properties to opt out of
inclusion in synthesized `TangentVector` structs.
Some stored properties cannot be used in `TangentVector` struct synthesis and
are implicitly marked as `@noDerivative`, with a warning:
- `let` stored properties.
- These cannot be updated by `mutating func move(along: TangentVector)`.
- Non-`Differentiable`-conforming stored properties.
`@noDerivative` also implies `@_semantics("autodiff.nonvarying")`, which is
relevant for differentiable activity analysis.
Add type-checking and SILGen tests.
Resolves TF-845.
